Many relatively simple electronic systems do not use virtual memory. For example, an inexpensive mobile phone may have a real-time operating system (RTOS) that maps all available physical memory directly into the virtual memory space of a processor. This is a simple solution that decreases the complexity of the system as compared to systems that incorporate virtual memory.
Since non-virtual memory systems have a “flat” memory map and do not swap pages of memory between different memory types, they typically include enough random access memory (RAM) to support the largest expected RAM requirement while the system is operating, whereas virtual memory systems can include less RAM since some memory contents may be paged out to nonvolatile memory. Tradeoffs are made between the cost of extra RAM and the cost of adding virtual memory capability to the system.